Nowadays, liquid crystal displays (LCDs) are generally packaged by using the chip on film (COF) packaging technology because the LCDs must be made to have high resolution and flatness and a narrow screen frame. The COF is the carrier package that joins the chip and the flexible circuit board.
Referring to FIG. 1 and FIG. 2 together, a COF 100 comprises a main body area 110, an input pin side 120 and an output pin side 130. The main body area 110 has a driving integrated circuit (IC) 112 disposed thereon. The COF 100 comprises an adhesive base layer 140, an adhesive layer 150, a copper layer 160 and a green paint layer 170 in sequence. The adhesive base layer 140 is located under the driving IC 112; the adhesive layer 150 is located under the adhesive base layer 140; the copper layer 160 is located under the adhesive layer 150; and the green paint layer 170 is located under the copper layer 160.
When the COF 100 is thermally pressed to a glass substrate (not shown) of the LCD, it is likely that a portion of the glass substrate in the bonded area becomes deformed or uneven relative to other portions of the glass substrate outside the bonded area due to the heat and pressure. This leads to a difference in transmissivity between the bonded area and the unbounded area of the glass substrate and, consequently, a difference in luminance presented by the LCD, which will adversely affect performance of the LCD.